You might be asked admin ussername and password. By default these units have username: "admin", and password "admin" (do not type in quotes).
These are settings that can be changed so if you changed yours before and cannot remember, you can reset the unit by pressing reset button and holding it for 30 seconds. That should restore default values.
On some websites I saw people mentioning combination username: "admin", password to be "password".
On this unit I obtained it was admin/admin.